Today, due to the lack in availability of petroleum oils, the trend towards Alternate Fueled Vehicles (AFV's), hybrid vehicles, and human powered vehicles (HPV's) has been the focus of many automakers, scientists, and inventors. Most of the automobile manufacturers are venturing into the area of the hybrid vehicles which utilize electric power in combination with the typical internal combustion engine. These hybrid vehicles present several drawbacks. First, these hybrid vehicles require heavy duty batteries to produce power. These batteries are heavy and require frequent charging, which limits the longetivity and feasibility of these vehicles.
Alluding to the above, a bicycle is another form of AFV's. Various bicycle configurations have been proposed to enhance the nexus between human power and kinetic energy. For example, numerous prior art patents have been proposed in which a hydraulic brake/transmission is incorporated into a bicycle, or for example electric/hydraulic motor vehicle braking is provided to create regenerative energy storage for conversion into kinetic energy.
In a standard bicycle setup, braking traditionally operates on the principle of a clamping caliper with opposing pads frictionally engaging the rotating wheel rim to convert the kinetic energy of the bicycle into heat through the mechanism of friction. Thus, valuable kinetic energy is thrown away as lost heat during braking. The goal of the regenerative hydraulic braking bicycle project is to reduce the amount of energy required from the rider to accelerate the bike to 20 mph. When the rider engages the regeneration cycle for deceleration during braking, a hydraulic pump directs fluid to a nitrogen-filled accumulating tank and stores energy in the form of pressurized nitrogen in the accumulating tank. When the rider wants to accelerate again, he/she runs the launch cycle, which uses a hydraulic motor to release the pressure in the tank and convert the stored energy to torque on the front wheel of the bicycle. Ideally, the pressure stored in the tank will provide enough energy to return the bike to its original speed before the regeneration cycle. In addition, past bicycles have only utilized a single option for braking during the regeneration cycle.
The U.S. Pat. No. 4,087,105 to Amarantos, for example, suggests the use of a hydraulic system to replace sprockets and a chain in a bicycle, and which provides a secondary ability to store braking energy for later use in an accelerated launch. This system is installed on a back wheel of the bicycle and the entire bicycle is built around this hydraulic system. The accumulator and low side reservoir are located in the frame of the bicycle itself. The U.S. Pat. No. 4,087,105 to Amarantos uses two pumps and no chain. Propulsion must be carried out entirely by the hydraulic system. A first hydraulic pump is attached to the pedal crank, so that as the rider pedals, he or she effectively turns the pump. Fluid flows to the hydraulic motor on the rear wheels and turns the wheel in lieu of a chain. When stopping or going down hill, a valve can be switched to allow fluid to flow into an accumulator and increase in pressure, because the motor is free spinning. The second pump is activated by the rider pumping on a handlebar in an up-and-down motion. This causes pressure in the accumulator to increase. Braking is accomplished by stopping the fluid flow from the motor to the reservoir. As the fluid flow is cut off, the back pressure increases thus stopping the fluid and locking the rotation of the motor.
The U.S. Pat. No. 4,087,105 to Amarantos's proposal is deficient in numerous respects. First, the system relies upon the hydraulic system and the rider's pedaling input to move the bike forward. Thus, the energy losses inherent in the pump and the motor will result in significant over-exertion. Second, restricting the fluid flow out of the pump/motor may vary the braking, but will not vary the amount of energy regenerated. Thus, it would be a misnomer to suggest the system disclosed in the U.S. Pat. No. 4,087,105 to Amarantos actually achieves variable regenerative braking. Furthermore, this system requires a specially designed bicycle, and is not capable of retro-fit installation in an existing bicycle. Also, a 0-20 mph acceleration for 220 pounds required nearly 5000 Joules of energy storage, and using the standard 4000 psi pumps, the fluid volume proposed in the U.S. Pat. No. 4,087,105 to Amarantos is severely underestimated.
Another example of a prior art system is taught by the U.S. Pat. No. 4,942,936 to Gardner, which describes a bicycle capable of running off either compressed air or hydraulic fluid from a pump powered by an electric motor. The bicycle has the typical chain and sprocket assembly to function as a normal bicycle when needed. The bicycle has regenerative braking accomplished by a generator that continuously puts energy back into a battery, which in turn is used to operate the hydraulic motor. This concept is deficient in that the hydraulic (or pneumatic) system does not directly generate the energy. Rather, the electric generator supplies energy to the battery which in turn powers the motor that drives the pump. Not only do these additional components increase system complexity, weight and cost, but the numerous energy conversions introduce losses which are proportionally significant in a bicycle application. Furthermore, this prior art design places propulsion units at both wheels, thereby further increasing the weight of the bicycle system. Also, to achieve a mildly aggressive braking at 20 mph of 4 m/s2 deceleration, an electric motor greater than 4 hp would be required. The added weight of a 4 hp efficient electric motor would make it an unacceptable solution for a bicycle.
Other examples of prior art systems may include hydraulic bicycle brakes and transmissions, such as those depicted in the U.S. Pat. Nos. 5,938,224 and 5,772,225. These devices provide an interesting way to transmit power to the wheels instead of using a chain, but provide no capability for energy storage. In addition, the U.S. Pat. No. 6,032,968 discloses a hydraulic transmission for a bicycle. Other examples of hydraulic powered bicycle brakes may be found in the U.S. Pat. Nos. 5,813,501 and 5,082,093. Examples of hydraulic regenerative braking may be found in numerous motor vehicle examples in which the braking energy is converted into electricity. This can be done with either direct connection to the vehicle brake system through a mechanical interchange, or via a hydraulic pump mounted at each wheel.
But even, if it is practicable, it would be desirable to provide an improved regenerative braking system for a vehicle, such as, for example, a bicycle, and the like, configured to recapture part of the kinetic energy that would otherwise be lost when braking and make use of that power released to assist take-off and hill climb maneuvers of the bicycle.
As such, the Applicant's inventive concept is aimed to solve one or more problems associated with the prior art designs.